String file_path = “your file from your file system “;
System.out.println(“File to upload ” + file_path);
FileInputStream fis = null;
try {
   File file = new File(file_path);
   if (!file.exists() || file.length() == 0) {
       Utils.stampaLogE(“Conversion Hash SHA-256 . Bad input !!! ( File not found / File empty)…”);
       throw new RuntimeException(“Conversion Hash SHA-256 . Bad input !!! ( File not found / File empty       )…”);
    }
    fis = new FileInputStream(file);
    byte[] fileBytes = new byte[(int) file.length()];
    MessageDigest md = MessageDigest.getInstance(“sha-256”);
    int length;
    while ((length = fis.read(fileBytes)) != -1) {
        md.update(fileBytes, 0, length);
    }
    byte[] raw = md.digest();
    StringBuilder sb = new StringBuilder();
    String base64 = Base64.encode(raw);
    return base64;
    } catch (Exception e) {
       e.printStackTrace();
       throw e ;
    } finally {
       if (fis != null) {
           try {
               fis.close();
           } catch (IOException e) {              
               e.printStackTrace();
          }
      } 
}